Types of keys

The cryptographic keys are grouped into the following categories based on the functions that they perform.

Symmetric keys master key (SYM-MK)

The SYM-MK master key is a triple-length (192-bit) key that is used only to encrypt other DES keys on the coprocessor. The administrator installs and changes the SYM-MK master key using the panel.exe utility, the clear key entry panels, the z/OS® clear key entry panels, or the optional Trusted Key Entry (TKE) workstation. The master key always remains within the secure boundary of the coprocessor. It is used only to encipher and decipher keys that are in operational form.

Note: If the coprocessor is shared with z/OS, the SYM-MK key must be a double-length (128-bit) key. This means that the first 64 bits and the last 64 bits of the key must be identical. If the master key is loaded by z/OS CCA or from a TKE workstation, it will automatically be a double-length key.

AES keys master key (AES-MK)

The AES-MK master key is a 256-bit key that is used to encrypt other AES keys and HMAC keys on the coprocessor. The administrator installs and changes the AES-MK master key using the panel.exe utility, the clear key entry panels, the z/OS clear key entry panels, or the optional Trusted Key Entry (TKE) workstation. The master key always remains within the secure boundary of the coprocessor. It is used only to encipher and decipher keys that are in operational form.

Asymmetric keys master key (ASYM-MK)

The ASYM-MK is a triple-length (192-bit) key that is used to protect RSA private keys on the coprocessor. The administrator installs and changes the ASYM-MK master key using the panel.exe utility, the clear key entry panels, the z/OS clear key entry panels, or the optional Trusted Key Entry (TKE) workstation. The master key always remains within the secure boundary of the coprocessor. It is used only to encipher and decipher keys that are in operational form.

AES CIPHER keys

The AES cipher keys are 128-bit, 192-bit, and 256-bit keys that protect data privacy. If you intend to use a cipher key for an extended period, you can store it in key storage so that it will be re-enciphered if the master key is changed.

AES PKA master key (APKA-MK)

The APKA-MK key, introduced to CCA beginning with Release 4.1.0, is used to encrypt and decrypt the Object Protection Key (OPK) that is itself used to wrap the key material of an Elliptic Curve Cryptography (ECC) key. ECC keys are asymmetric. The APKA-MK is a 256-bit (32-byte) value. The administrator installs and changes the APKA-MK master key using the panel.exe utility, the clear key entry panels, the z/OS clear key entry panels, or the optional Trusted Key Entry (TKE) workstation.

Data-encrypting keys

The data-encrypting keys are single-length DES (64-bit), double-length DES (128-bit), or triple-length DES (192-bit) keys, or 128-bit, 192-bit or 256-bit AES keys that protect data privacy. Single-length DES data-encrypting keys can also be used to encode and decode data and authenticate data sent in messages. If you intend to use a data-encrypting key for an extended period of time, you can store it in the CCA key storage file so that it will be re-enciphered if the master key is changed.

You can use single-length DES data-encrypting keys in the Encipher and Decipher verbs to manage data, and also in the MAC Generate and MAC Verify verbs. Double-length DES and triple-length DES data-encrypting keys can be used in the Encipher and Decipher verbs for more secure data privacy. DATAC is also a double-length DES data encrypting key.

AES data-encrypting keys can be used in services similar to DES data-encrypting key services.

DES CIPHER keys

These consist of CIPHER, ENCIPHER, and DECIPHER keys. They are single and double length DES keys for enciphering and deciphering data.

Ciphertext translation keys

These ciphertext translation keys consist of CIPHERXI, CIPHERXL, and CIPHERXO keys. They protect data that is transmitted through intermediate systems when the originator and receiver do not share a common key. Data that is enciphered under one ciphertext translation key is re-enciphered under another ciphertext translation key on the intermediate node. During this process, the data never appears in the clear. These keys are double-length.

HMAC keys

HMAC keys are variable-length symmetric keys. The length is in the range of 80 - 2024. HMAC keys are used to generate and verify HMACs using the FIPS-198 algorithm, with the HMAC Generate and HMAC Verify verbs.

• Operational keys will be encrypted under the AES master key
• HMAC keys can be imported and exported under an RSA key.
• HMAC keys will be stored in the AES key storage file. The AES master key must be active.

For more information about HMAC keys and verb processing, see Verifying data integrity and authenticating messages.

MAC keys

The MAC keys are single-length DES (64-bits - DATAM, DATAMV, MAC, and MACVER, ) and double-length DES (128-bits - DATAM, DATAMV, MAC, and MACVER) keys used for the verbs that generate and verify MACs.

PIN keys

The personal identification number (PIN) is a basis for verifying the identity of a customer across financial industry networks. PIN keys are used in cryptographic functions to generate, translate, and verify PINs, and protect PIN blocks. They are all double-length DES (128 bits) keys. PIN keys are used in the Clear PIN Generate, Encrypted PIN Verify, and Encrypted PIN Translate verbs.

For installations that do not support double-length DES 128-bit keys, effective single-length DES keys are provided. For a single-length DES key, the left key half of the key equals the right key half.

Processing personal identification numbers gives an overview of the PIN algorithms you need to know to write your own application programs.

AES transport keys (or key-encrypting keys)

Transport keys are also known as key-encrypting keys. They are used to protect AES and HMAC keys when you distribute them from one system to another.

There are two types of AES transport keys:

Exporter key-encrypting key

This type of key protects keys of any type that are sent from your system to another system. The exporter key at the originator is the same key as the importer key of the receiver.

Importer key-encrypting key

This type of key protects keys of any type that are sent from another system to your system. It also protects keys that you store externally in a file that you can import to your system at another time. The importer key at the receiver is the same key as the exporter key at the originator.

DES transport keys (or key-encrypting keys)

Transport keys are also known as key-encrypting keys. They are double-length (128 bits) DES keys used to protect keys when you distribute them from one system to another.

There are several types of DES transport keys:

Exporter or OKEYXLAT key-encrypting key

This type of key protects keys of any type that are sent from your system to another system. The exporter key at the originator is the same key as the importer key of the receiver.

Importer or IKEYXLAT key-encrypting key

This type of key protects keys of any type that are sent from another system to your system. It also protects keys that you store externally in a file that you can import to your system later. The importer key at the receiver is the same key as the exporter key at the originator.

NOCV importers and exporters

These keys are key-encrypting keys used to exchange keys with systems that do not recognize key-encrypting key variants. There are some requirements and restrictions for the use of NOCV key-encrypting keys:

• The use of NOCV IMPORTERs and EXPORTERs is controlled by access control points in the coprocessor's role-based access control system.
• Only programs in system or supervisor state can use the NOCV key-encrypting key in the form of tokens in verbs. Any program can use NOCV key-encrypting keys with label names from the key storage.
• Access to NOCV key-encrypting keys should be carefully controlled, because use of these keys can reduce security in your key management process.
• NOCV key-encrypting key can be used to encrypt single or double length DES keys with standard CVs for key types DATA, DATAC, DATAM, DATAMV, DATAXLAT, EXPORTER, IKEYXLAT, IMPORTER, IPINENC, single-length MAC, single-length MACVER, OKEYXLAT, OPINENC, PINGEN and PINVER.
• NOCV key-encrypting keys can be used with triple length DATA keys. Because DATA keys have 0 CVs, processing will be the same as if the key-encrypting keys are standard key-encrypting keys (not the NOCV key-encrypting key).

Note: A key-encrypting key should be as strong or stronger than the key that it is wrapping.

You use key-encrypting keys to protect keys that are transported using any of the following verbs: Data Key Export, Key Export, Key Import, Clear Key Import, Multiple Clear Key Import, Key Generate, Key Generate2, Key Translate and Key Translate2.

For installations that do not support double-length key-encrypting keys, effective single-length keys are provided. For an effective single-length key, the clear key value of the left key half equals the clear key value of the right key half.

Key-generating keys

Key-generating keys are double-length keys used to derive other keys. This is often used in smart card applications.

Clear keys

A clear key is the base value of a key, and is not encrypted under another key. Encrypted keys are keys whose base value has been encrypted under another key.

To convert a clear key to an encrypted data key in operational form, use either the Clear Key Import verb or the Multiple Clear Key Import verb.